KickboxingCrazy

iTrader: (15)

recently got a MY99 STi redtop V5. ive been driving it and it didnt feel like it was running much boost, definatly not 280bhp (cars completely standard)

put a boost guage in today and its only running 7psi, anyone no why?

i thought STi should run 12psi

Splitpin

Yeah, a technician looking at your engine will know. Only so much we can do via the power of the interwebs. At the moment all we can do is assume that the car is, as you say, bog standard. That assumption may be wrong for all we know.

The likeliest explanation (albeit one of many possible explanations), if it its consistently running 7psi and no higher, is that the ECU is in limp/boost disable mode, either due to excessive knock or another problem.

Is the check engine light illuminated, or have you seen it light up at all during the time you've had the car? If not, in an ideal world you'd get it on a Select Monitor (or emulator). If that's not an option, in the first instance, try connecting the black plugs and checking for stored error codes. If none, try resetting the ECU - although I'd personally be dubious about taking that step without diagnosing the car properly in its current form, and installing some standalone knock monitoring.


Incorrect. Peak target boost on an STi version 5 is 1.08 bar - 15.66psi

KickboxingCrazy

iTrader: (15)

hello there, thanks for the reply, im a mechanic and have had stacks of well tuned cars that i have built myself, the car has still got standard exhaust ect.. no engine light on, i tried my det cans today and it was fine (chances of getting det at 7psi are minimal) its running 99 ron. no manual controller, all pipework to standard solinoid intact. the car pulls lovely to the limiter with no miss firing, its defo not in limp mode.

so it should be running just over a bar. thanks alot

Splitpin

I didn't say you would be getting det at 7psi. What I was saying is that if it dets too much at the standard boost limit, and the ECU can't pull enough timing to eliminate it, it will eventually disable boost completely.

Comments about fuel choice etc noted - fact remains that you're still running below the octane rating your car is mapped for, and you also presumably don't know at this point how healthy or otherwise the airflow sensor is. And no, they often don't cause an error even if seriously degraded.

You have no way of knowing for certain whether it is or not unless you've diagnosed the ECU. The fact that it is running 7psi suggests that it's running actuator pressure. If it's running actuator pressure, either the boost has been disabled or, for some reason, either the ECU can't control the solenoid (which should raise error code no. 44) or the solenoid can't control the boost. One thing to check would be that the restrictor pill is in the pipe between the compressor outlet and t-piece. If a previous owner has removed it for some reason, you could get what you're experiencing.

Should be, yes.

KickboxingCrazy

iTrader: (15)

right thanks alot splitpin, is there any way of resetting the ecu?(does taking the battery supply trick work) ill do some tests on sensors today, ill check the pill also.

is there any tests i can do on the air sensor

Davros 1979

iTrader: (56)

This should help you:

JollyGreenMonster.co.uk

KickboxingCrazy

iTrader: (15)

okay ill give that a try now

Splitpin

The link to the black plug memory read process given to you by Davros is the first thing to do. At least then you'll be able to see whether there are any stored errors.

Pulling the battery will reset, but the better way to do it is to look up the "black plug and green plug" process. Resetting the ECU this way runs a test on the internal sensors and solenoids and will only flash the "all clear" on the CEL when they have all "passed". The only problem with this is that, as mentioned above, some of the sensors, the MAF sensor in particular, can degrade dangerously without the ECU being able to detect it.

Re. the airflow meter, the only way to test properly on the move is with a select monitor (or emulator) plugged in and the output being checked and compared with MAP and engine speed.

You can connect a voltmeter direct to the sensor output - but this approach is limited, especially if your meter doesn't have a very fast update rate, as it won't accurately detect the voltage dropping out.

Also note that some will tell you that you can test the sensor by disconnecting it with the engine running and seeing if the engine stalls. This, unfortunately, is a Scoobynet old wives' tale and doesn't give results that make any sense (or can be trusted), and can also damage good sensors.

The other test is to get a brand new sensor and compare (ideally with diagnostic help) the car's behaviour with the new sensor and the old one.

KickboxingCrazy

iTrader: (15)

right update.

done the test on the sensors, engine light flash with 1 second gaps to indicate all clear.

i checked the actuator to boost controller piping and it looks original, is this pill inside the hoseing? (ie a hard plastic restrictor) or is it visable, a pic would be great

Splitpin

Don't have a pic here but shouldn't be necessary. Look at the pipe approx 2" long that runs between the compressor bleed air outlet and the t-piece. Pinch it all the way along its length and you should be able to feel the restrictor inside the pipe. It's a piece of brass about 5mm in diameter and 6mm long.

Also note that if you did the black and green plug routine earlier, your ECU will now be reset, so you should get full boost at very least the first time you floor it. If it's still stuck around the 0.7 bar area I'd check for the presence of the restrictor, and if that is there, check whether the pipework leading to the solenoid, and from the solenoid back into the inlet tract, has become blocked.

KickboxingCrazy

iTrader: (15)

ill check all that tomorow. cheers

KickboxingCrazy

iTrader: (15)

right, heres a quick diagram of my boost setup.


isit right for the standard valve?

theres only one restrictor init. shouldnt there be one going to the solinoid too

Splitpin

There should only be the one restrictor, exactly where you've found it, so that bit's correct.

However, are you sure you've drawn it accurately? You've got the return pipe from the solenoid going into the inlet manifold. Is that really where it goes? If so, it shouldn't, it should run into a rubber 90 degree bend which runs into the turbo inlet pipe that goes under the manifold.

Double check that you've got that right, as you may be confusing the solenoid return with the MAP sensor pipe (which should run into the manifold). If your drawing's correct, that almost certainly explains your problem.

KickboxingCrazy

iTrader: (15)

yer sorry that bit was wrong, it goes to the intake pipe.

this is abit annoying, i cant see why its not running the boost, i could just attach one of my bost controllers to it but i wana no why it aint running it standard first

Splitpin

Darn, was hoping we'd found the explanation there. You're thinking right re. not fitting a boost controller. If the ECU is in boost disable, it will be doing it for a reason, so working around it with an external BC is asking for trouble at least until you know what's what.

The one good thing is that the list of possible causes is dwindling.

Check that the pipes between the t-piece and solenoid, and the return from the solenoid to turbo pipe aren't blocked with oily gunk. Then put the ECU in test mode (green plugs only and ignition on search for more info if necessary). This will make the solenoid open and close - so check first of all that you can feel it actually clicking and secondly that you can blow through it when it's open. Spray it through with brake cleaner if not.

Also make absolutely certain that there are no leaks in the pressurised side of the induction tract - from turbo outlet through the intercooler to the throttle body.

Long shot but I'd also poke the restrictor out and make sure it's the right size (off top of head the orifice should be 0.8mm, but double check that). Not impossible that previous owner has lost the right one and shoved something else up there. Unlikely but a quick and easy thing to rule out.

If none of those turns up anything obvious, you'll save a lot more time and headscratching by getting the car on a select monitor (or similar).

KickboxingCrazy

iTrader: (15)

yea i was thinking that.

i renewed one of the pipes today as it became brittle, i might do the rest aswell to make sure,ill quickly get the solinoid of now.

ive checked power to it, all there

when i used to fit 2 stage boost, in off mode it would run half boost, so am thinking there could be something up with the solinoid. worth a look.

ecu checks all clear again

KickboxingCrazy

iTrader: (15)

right standard solinoid is not clicking, so i suspect this is at fault, ive overrid it tempory to see see if this was the problem and im getting around 13psi, wont runn it like this but i wondering why the ecu aint picking the fault up

Splitpin

Ah, good, getting somewhere. The ECU will (if I remember right) only trigger DTC 44 if the loom between it and the solenoid goes open circuit. You can test that relatively easily by unplugging the BCS. Should get instant CEL with code 44 (four long flashes, four short) when you do the black plugs.

It sounds as though the coil is still good but the plunger is gummed up with something. Brake cleaner probably still worth a try, while looking around for a spare 99-00 (might be okay with an MY01 or MY02 newage) solenoid.

KickboxingCrazy

iTrader: (15)

okay so basically it wont pick up a mailfunction just a open circuit.

this looks identical but ill have to check part numbers

(103) 2001 Subaru Impreza WRX Boost Sensor on eBay (end time 02-Nov-09 11:08:34 GMT)

Splitpin

AA160, yeah that's the one, although whether you want to pay that sort of money for one in that sort of nick is another question altogether.

KickboxingCrazy

iTrader: (15)

i was thinking the same. silly money

KickboxingCrazy

iTrader: (15)

right, update.

took the solinoid off today and tested it, cleaned it with carb cleaner.

when i put a good earth a live to it direct from battery it clicks, so the solinoids okay, i worked out it was the earth that wasnt working, re wired the earth up and it clicked fine but the engine check light came on (ran an earth into the existing earth) bloody annoying.

KickboxingCrazy

iTrader: (15)

up.